1. Field of the Invention
The present disclosure relates to measurement systems, and more particularly to measurement systems employing bridge circuits.
2. Description of Related Art
A bridge circuit generally includes resistors arranged in two parallel branches between voltage terminals. Each branch generally includes two resistors arranged in series, an intermediate terminal disposed between the resistors, and a ‘bridging’ branch connecting the intermediate terminals. Typically, one resistor in each parallel branch has a known resistance, a third resistor in one parallel branch has an adjustable variable resistance, and a fourth resistor in the other parallel branch has unknown resistance. By adjusting the variable resistance of the third resistor such that no current flows through the ‘bridging’ branch the unknown resistance of the fourth resistor can be determined. This is because the ratio of the fixed resistance of the first resistor and the variable resistance of the third resistor is the same as a ratio of the fixed resistance of the second resistor and the unknown resistance of the fourth when no current flows through the ‘bridging’ branch. By arranging the fourth resistor such that its resistance varies with a parameter of interest, the parameter can be measured by determining the resistance of the fourth resistor.
One challenge to sensors incorporating such bridge circuits is the influence of unrelated factors on the measured resistance. For example, some bridge circuits can be susceptible to high impedance leakage due to the common mode voltage created at the intermediate terminals. Since the circuit output is not typically a low impedance source, high impedance leakage can cause output changes that can be confused with resistance change due to change in the parameter of interest.
Such conventional systems and methods have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved sensor interface circuits. The present disclosure provides a solution for this need.